Accelerator Controls

Part2: CERN central timing system

CAS 2009@Divonne

Hermann Schmickler

Outline Part 2

• Requested Functionality of the CERN timing system

• Implementation:

Hardware Details

Software Details:

- definition of terms

- applications

- tools

• Summary

Demanded Functionality of the Timing System

• In general: Stimulate the creation of any particle

beam type and assure the proper sequence of

transport and acceleration througout the chain.

• In each machine or transport line:

Sequence or synchronize the time development of

every equipment down to the level of the micro-s.

• Provide absolute time information and time

stamping of data down to the level of ns.

• Function as a unidirectional broadcast system for

machine flags or safety information.

R1

LHCCNGS

Linac PSB CPS SPS

D3

Dump

TI8

Dump

TI2

DumpSPS

Dump

R2

LHC

TCLP

The LHC Proton Injector Chain

Strongly time coupled

CERN accelerator network

sequenced by central timing generator

….…. ….….

PSB

CPS

SPS

LHC

Experimental

area

Experimental

area

Experimental

Area

CBCM Sequence Manager

PSB1 PSB1 PSB2PSB2 PSB3PSB3 PSB4 PSB4

CPS Batch 1 CPS Batch 2 CPS Batch 3 CPS Batch 4

SPS Cycle for the LHC

SPS injection plateaux

The LHC Beam

LSA Beam request:

RF bucket

Ring

CPS batches

Extraction

Forewarning

LHC Injection plateaux

Injection Injection

ExtractionExtraction

The LHC timing is only

coupled by extraction

start-ramp

event

Extraction

Forewarning

Hardware Implementation of CBCM

• At a single central place (CCR-Prevessin) we have the master timing

generator (CBCM = central beam cycle manager), which generates the

clock-beat and all relevant sequence information.

There is a hot spare system running all the time.

• Through reflective memory the generated information is shared with

the individual timing generator chassis for each machine.

• From these machine timing generators the information leaves on a

cable/fibre optics links at a 1ms interval.

GPS

One pulse

per Second

GPS

Smart clock

PLL

PLL

One pulse

per Second

Phase locked

10MHz

Basic Period

1200/900/600 ms

Advanced (100us)

One pulse

per Second

Synchronized 1KHz

(slow timing clock)

Phase locked

10MHz

Phase looked

40 MHz Event

encoding clock

40MHz PLL

CTSYNC

RS485

Timing

CTGU

The

new

generation

low

jitter <1ns

VME

based

MTG

module

UTC time (NTP or GPS)

Event

tables

External events

Hardware developments CTG

and CTR

CERN

UTC

Time

Set once on startup

& on Leap Seconds

RS485

Timing

CTRP

40 MHz

10 MHz

1 KHz

1PPS

Delay

Control SystemCERN

UTC

Time

25ns steps

Timing receiver

Hardware II

LHC MTG

2.2 G-Bit / S optical link

64Mb Reflective memories

Main MTGLHC MTG

BST

GMT

LHC

CPS and SPS telegrams and timings

and MTG synchronization when filling

Clocks:

Bunch Clock 40..8 MHz.

Frev ticks at 89us.

40.00 MHz GPS clock

1PPS (1Hz) clock

Basic period clock

Preloaded

Injector

Sequences

Preloaded

LHC

Sequence

3 BST

Cards

Safe

Params

Energy/Ring

Intensity/Ring

Safe Beam Flg

Beam present Flg

Extraction permit Flg

BIC Beam permit Flg

External Conditions

and Events

Hardware Implementation

• …and at the other end of the timing cable:

• Receiver modules in different form factors;

here shown in VME

- reception of timing information

- programmed reaction to specific

timing events

- reconstitution of clock references

- programmable hardware outputs

for integration into system

- programmable software interrupts

for system host

Outline Part 2

• Requested Functionality of the CERN timing system

• Implementation:

Hardware Details

Software Details:

- definition of terms = lots of TLA or FLAB

- applications

- tools

• Summary

Terminology: The Telegram

• It is a set of parameters group values (PARTY=PROTON, DEST=FTS,….) describing what each accelerator should do now.

• Each accelerator telegram layout is different

• Describe the present and the next cycle

• Telegrams drive the PPM/Multiplexing and SPS Multi-cycling

• They are delivered each basic period. (Currently 1BP = 1.2S)

Terminology: The basic period

• The basic unit of time use to define cycles.

Characterized by :

– a duration of 1.2s (Can be changed)

– a telegram (32 parameters/groups maximum)

– all cycle and super-cycle durations are a

multiple of this time

– is the heart beat of the central timing

Terminology: The CYCLE

• Set of basic period

– Length = N x Basic Period

– Static telegram groups • Their values don’t change within a cycle (USER=SFTPRO)

• They are mostly calculated at BCD build time offline

– Dynamic telegram groups• Their values can change from a basic period to another

within a cycle (BPNM=1)

• They are sometimes calculated in real time

USER=EASTA, PARTY=PROTON,BPNM=1

EASTA Cycle

USER=EASTA, PARTY=PROTON,BPNM=2

Basic periods

Terminology: The BEAM• Link cycles together

(same/different accelerators)

– When a beam is played by

MTG, all cycles of the beam

will be played.

– The basic unit of work for the

central timing

– Decisions taken by the MTG

on what to do next are based

on beams

• Defined by :

– Set of cycles

– Phase between cycles

Strong and Loose coupling

Strong Coupling

• Same supercycle

length

• Cycles are strongly

connected to create a

beam

• Free supercycle

phase

Loose Coupling

• Free supercycle

length

• RT synchronization

with machine in

strong coupling for

beam injection

• Supercycle can be

stopped

• Occasional injection

Terminology: NORMAL/SPARE

• Maximize accelerator up-time.

Terminology:

NORMAL/SPARE(2)• Representation in software tools

ZERO

PSB

CPS

SFTPRO

ISOGPS

SFTPRO

Normal

Normal

Spare

Spare

Sequences

Lead-In

Pulse-Start to

14Gev

Main Sequence for Fixed

Target

Lead-Out

Pulse Stop

Lead-In

Pulse Start to

26Gev

Main Sequence for LHC filling Lead-Out

Pulse Stop

Fixed

Target

LHC Fill

Repeat

Level

Switch

Sequence Change

Main Lead-out

Eject

Ramp

Pulse Stop

32 Levels

Lead-inCoast

Pulse Start

Inject, Ramp

LHC Fill

request

External Conditions• Comprised of Requests, Inhibits, Interlocks.

• They are logic levels 1=Bad, 0=Good

• They control the CBCM

– Normal <-> Spare

– Sequence selection

– BCD termination

• Can be either hardware or software

• Used By FIDO (= real time timing command interpretor)

to make decisions on what to do next

FiDo programs

• MTG integrates the compiler and the interpreter.

• Can be downloaded in real-time

Beam Coordination Diagram editor

Strong Coupling

Loose coupling ADEInjection

rendezvous

pointsStart point Function points Eject antiprotons

Cooling

Make MTG table

BCD

The BCD is the result of the merging of BCDs produces by the two editors.

BCD Editor: Rule checker

Sequence manager

MTG diagnostic

CTIM (2)

Timing events (CTIM) (3)

• Controllable by knobs in real-time

Virtual event

Key events

Summary Part 2

• The CERN timing system is an almost unique technical

solution to a very complex timing/sequencing problem. Only

a few accelerator centers in the world are confronted with its

complexity of operation.

• The functionality/hardware implementation has evolved over

the past decades. Lots of legacy equipment has still to be

supported.

• Presently a project is under way in order to:

- simplify hard- and software

- increase functionality (higher resolution, bidirectional

information)

- name: White Rabbit please visit BE-CO-HT webpages